U.S. patent number 7,768,964 [Application Number 12/221,444] was granted by the patent office on 2010-08-03 for method of operating a mobile wireless network.
This patent grant is currently assigned to IPCOM GmbH & Co. KG. Invention is credited to Mark Beckmann, Martin Hans.
United States Patent |
7,768,964 |
Hans , et al. |
August 3, 2010 |
Method of operating a mobile wireless network
Abstract
A method of operating a mobile wireless network is provided, in
which, when there is a relocation, the connection may be continued
essentially directly from the latest state before the relocation.
User data is transmitted between a mobile station and a first base
station, the user data being combined into data units, for example,
packet data units, before being transmitted. For transmission of
data units, transmission-specific information describing an
instantaneous state of the transmission is stored in the mobile
station, as well as in a first network unit at a higher level than
the first base station. With the relocation of the mobile station
from the first base station to a second base station having a
second higher-level network unit, the transmission-specific
information stored in the first higher-level network unit is
transmitted to the second higher-level network unit to continue the
transmission after the relocation essentially directly from its
latest state.
Inventors: |
Hans; Martin (Hildesheim,
DE), Beckmann; Mark (Braunschweig, DE) |
Assignee: |
IPCOM GmbH & Co. KG
(Pullach, DE)
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Family
ID: |
26005208 |
Appl.
No.: |
12/221,444 |
Filed: |
August 1, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080291877 A1 |
Nov 27, 2008 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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10130867 |
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7453838 |
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PCT/DE00/03758 |
Oct 25, 2000 |
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Foreign Application Priority Data
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Nov 22, 1999 [DE] |
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199 56 062 |
Apr 5, 2000 [DE] |
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100 17 062 |
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Current U.S.
Class: |
370/328 |
Current CPC
Class: |
H04W
36/12 (20130101); H04W 36/08 (20130101); H04L
29/06 (20130101); H04L 69/324 (20130101) |
Current International
Class: |
H04W
4/00 (20090101) |
Field of
Search: |
;370/328,469 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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199 44 334 |
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Dec 2000 |
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DE |
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99 22557 |
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May 1999 |
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WO |
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99 41850 |
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Aug 1999 |
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WO |
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01 20938 |
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Mar 2001 |
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WO |
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Other References
3sup.rd Generation Partnership Project; Technical Specification
Group Radio Access Network; Packet Data Convergence Protocol (PDCP)
Specification (Release 1999). cited by other .
IETF, RFC 1144, Feb. 1990. cited by other .
IETF, RFC 2507, Feb. 1999. cited by other.
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Primary Examiner: Harper; Kevin C
Attorney, Agent or Firm: Kenyon & Kenyon LLP
Parent Case Text
RELATED APPLICATION INFORMATION
This application is a continuation application of U.S. patent
application Ser. No. 10/130,867, filed Oct. 7, 2002, now U.S. Pat.
No. 7,453,838 which is a U.S. national stage application of PCT
international application number PCT/DE00/03758 having an
international filing date of Oct. 25, 2000, designating the United
States of America, and which claims priority to and the benefit of
German Patent Application No. DE 199 56 062.5, filed in Germany on
Nov. 22, 1999, and of German Patent Application No. DE 100 17
062.5, filed in Germany on Apr. 5, 2000, the entire contents of all
of which are expressly incorporated herein by reference.
Claims
What is claimed is:
1. A method of operating a mobile wireless network within which
user data is transmitted between a mobile station and a first base
station, the user data being combined into data units prior to a
transmission of the data units, the method comprising: storing
transmission-specific information related to an instantaneous state
of the transmission of the data units in both the mobile station
and in a first network unit, the first network unit being at a
level that is higher than a level of the first base station; and
transmitting the transmission-specific information stored in the
first network unit to a second network unit of a second base
station when the mobile station relocates from the first base
station to the second base station, the second network unit having
a level that is higher than the level of the second base station to
continue the transmission of the data units after the mobile
station relocates from the first base station to the second base
station; wherein the data units include packet data units, and
wherein the first network unit further includes a first unit of a
first convergence protocol layer, the second network unit further
includes a second unit of a second convergence protocol layer, and
the transmitting of the transmission-specific information includes
transmitting the information via the first unit of the first
convergence protocol layer to the second unit of the second
convergence protocol layer when the mobile station relocates from
the first base station to the second base station.
2. The method according to claim 1, wherein during relocation, the
transmission-specific information in the first network unit and
data units intermediately stored for control purposes are
transferred to the second higher level network unit.
3. The method according to claim 1, wherein the transmitting of the
transmission-specific information includes transmitting over a
fixed network when the mobile station relocates from the first base
station to the second base station.
4. A method of operating a mobile wireless network within which
user data is transmitted between a mobile station and a first base
station, the user data being combined into data units prior to a
transmission of the data units, the method comprising: storing
transmission-specific information related to an instantaneous state
of the transmission of the data units in both the mobile station
and in a first network unit, the first network unit being at a
level that is higher than a level of the first base station; and
transmitting the transmission-specific information stored in the
first network unit to a second network unit of a second base
station when the mobile station relocates from the first base
station to the second base station, the second network unit having
a level that is higher than the level of the second base station to
continue the transmission of the data units after the mobile
station relocates from the first base station to the second base
station; wherein the data units include packet data units, and
wherein the data units include packet data units, and wherein
during relocation, the transmission-specific information in the
first network unit and data units intermediately stored for control
purposes are transferred to the second higher level network
unit.
5. The method according to claim 4, wherein the first network unit
further includes a first unit of a first convergence protocol
layer, the second network unit further includes a second unit of a
second convergence protocol layer, and the transmitting of the
transmission-specific information includes transmitting the
information via the first unit of the first convergence protocol
layer to the second unit of the second convergence protocol layer
when the mobile station relocates from the first base station to
the second base station.
6. The method according to claim 5, wherein the transmitting of the
transmission-specific information includes transmitting over a
fixed network when the mobile station relocates from the first base
station to the second base station.
7. A method of operating a mobile wireless network within which
user data is transmitted between a mobile station and a first base
station, the user data being combined into data units prior to a
transmission of the data units, the method comprising: storing
transmission-specific information related to an instantaneous state
of the transmission of the data units in both the mobile station
and in a first network unit, the first network unit being at a
level that is higher than a level of the first base station; and
transmitting the transmission-specific information stored in the
first network unit to a second network unit of a second base
station when the mobile station relocates from the first base
station to the second base station, the second network unit having
a level that is higher than the level of the second base station to
continue the transmission of the data units after the mobile
station relocates from the first base station to the second base
station; wherein the data units include packet data units, and
wherein the first network unit further includes a first unit of a
first convergence protocol layer, the second network unit further
includes a second unit of a second convergence protocol layer, and
the transmitting of the transmission-specific information includes
transmitting the information via the first unit of the first
convergence protocol layer to the second unit of the second
convergence protocol layer when the mobile station relocates from
the first base station to the second base station, and wherein the
transmitting of the transmission-specific information includes
transmitting over a fixed network when the mobile station relocates
from the first base station to the second base station.
8. A method of operating a mobile wireless network within which
user data is transmitted between a mobile station and a first base
station, the user data being combined into data units prior to a
transmission of the data units, the method comprising: storing
transmission-specific information related to an instantaneous state
of the transmission of the data units in both the mobile station
and in a first network unit, the first network unit being at a
level that is higher than a level of the first base station; and
transmitting the transmission-specific information stored in the
first network unit to a second network unit of a second base
station when the mobile station relocates from the first base
station to the second base station, the second network unit having
a level that is higher than the level of the second base station to
continue the transmission of the data units after the mobile
station relocates from the first base station to the second base
station; wherein the data units include packet data units, and
wherein the transmission-specific information in the first network
unit and data units intermediately stored for control purposes are
transferred to the second higher level network unit, and wherein
the first network unit further includes a first unit of a first
convergence protocol layer, the second network unit further
includes a second unit of a second convergence protocol layer, and
the transmitting of the transmission-specific information includes
transmitting the information via the first unit of the first
convergence protocol layer to the second unit of the second
convergence protocol layer when the mobile station relocates from
the first base station to the second base station.
9. The method according to claim 8, wherein the transmitting of the
transmission-specific information includes transmitting over a
fixed network when the mobile station relocates from the first base
station to the second base station.
Description
FIELD OF THE INVENTION
The present invention relates to a method of operating a mobile
wireless network.
BACKGROUND INFORMATION
German Published Patent Application No. 199 44 334 relates to a
method of operating a mobile wireless network, in which user data
is transmitted between a mobile station and a first base station,
the user data being combined into data units, for example, packet
data units, before being transmitted.
SUMMARY
It is believed that an exemplary method according to the present
invention is advantageous in that, for transmission of the data
units, transmission-specific information describing an
instantaneous status of the transmission is stored in both the
mobile station and in a first network unit at a higher level than
the first base station. When the mobile station changes connections
from the first base station to a second base station having a
second higher-level network unit, the transmission-specific
information stored in the higher-level network unit is transmitted
to the second higher-level network unit to continue the
transmission after the change in connection generally directly from
its instantaneous status. In this manner, the data units may be
continuously transmitted, regardless of a change in connection. It
may not be necessary to reset the transmission-specific information
to a starting state when changing connections. Thus, there may be
no impairment in the transmission capacity of the wireless
transmission between the mobile station and the second base station
may not be impaired after the change in connection is not impaired
by the transmission of data, this transmission capacity being
necessary to restore the transmission-specific information most
recently in effect in the second higher-level network unit.
It is believed to be advantageous in that control information is
added to the data units before being transmitted. The control
information is compressed by differential coding before
transmission, a code book being created in the mobile station and
in the first higher-level network unit for encoding and decoding
the control information, the two code books thus created having
identical contents, and the code book stored in the first
higher-level network unit being transmitted to the second
higher-level network unit with the transmission-specific
information when changing connection. In this manner, when changing
connection, the second higher-level network unit may receive
directly from the first higher-level network unit the code book
thus created in the mobile station and the first higher-level
network unit during the transmission of data units between the
mobile station and the first base station, so that the code book
need not be created or constructed after the change in connection,
thus making demands on the transmission capacity for transmission
between the mobile station and the second base station.
It is believed that another advantage is that, before or during
establishment of a connection for the transmission of data units
between the mobile station and the first base station, a first
signaling information is transmitted from the mobile station to the
first higher-level network unit to notify the first higher-level
network unit whether the transmission-specific information is to be
transmitted to the new higher-level network unit when changing
connection to a base station having a new higher-level network unit
different from the first higher-level network unit. Alternatively,
this first signaling information may be transmitted from the first
higher-level network unit to the mobile station, so the that
network may decide whether the transmission-specific information is
to be transmitted from the first higher-level network unit to the
new higher-level network unit. It is believed that this may be
advantageous because the first higher-level network unit has
information regarding the capabilities and resources of the new
higher-level network unit and regarding the fixed network
connection over which the transmission-specific information should
be transmitted. A selection option may provide, as needed, a
transmission of the transmission-specific information from the
first higher-level network unit to the new higher-level network
unit for a telecommunications connection to be established when
changing connection. In addition, the transmission-specific
information may be reset at a starting state after the change in
connection for the connection to be established. The exemplary
method according to the present invention is thus flexible in
use.
It is believed that another advantage is that, before or during the
change in connection, a second signaling information is transmitted
from the mobile station to the first higher-level network unit or
from the first higher-level network unit to the mobile station to
notify the first higher-level network unit or the mobile station
whether in this change in connection the transmission-specific
information is to be transmitted to the second higher-level network
unit. In this manner, even during a connection, a transmission of
the transmission-specific information from the first higher-level
network unit to the second higher-level network unit may be
provided for a telecommunications connection to be established, or
resetting of the transmission-specific information at a starting
state may be provided when changing connection, as needed, so that
an exemplary method according to the present invention may be
flexible in use.
It is believed that another advantage is that data units stored in
a buffer memory for control purposes in the first higher-level
network unit are transmitted to the second higher-level network
unit together with the transmission-specific information when there
is a change in connection. In this manner, data units needed for
checking the transmission of data units, for example, for
error-free transmission, and optionally stored in a buffer memory
and to be transmitted repeatedly, are not lost when there is a
change in connection.
It is also believed to be advantageous in that
transmission-specific information is transmitted over a fixed
network between the first higher-level network unit and the second
higher-level network unit when there is a change in connection. In
this manner, the data rate of the fixed network, which may be
higher, may be utilized for transmission of the
transmission-specific information, without making demands on the
transmission capacity of the mobile wireless network for this
transmission.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a mobile wireless network.
FIG. 2 is a block diagram showing a connection between a mobile
station and a first higher-level network unit over a first base
station before a change in connection.
FIG. 3 is a block diagram showing a connection between the mobile
station and the second higher-level network unit over a second base
station after a change in connection.
FIG. 4a is a compression table.
FIG. 4b shows a buffer memory for data units.
DETAILED DESCRIPTION
An exemplary embodiment according to the present invention relates
to a method of operating a mobile wireless network 1 according to
FIG. 1, in which there is a change in connection between two base
stations 25, 30, while a connection is established (also referred
to as "relocation"). Mobile wireless network 1 may be designed, for
example, according to the GSM standard (Global System for Mobile
Communications) or according to the UMTS standard (Universal Mobile
Telecommunications System). An exemplary method according to the
present invention refers to sending transmission-specific
information about the connection thus established, e.g., in the
form of internal protocol information to a convergence protocol
layer 130, 135 between two higher-level network units 50, 55 of
cellular mobile wireless network 1.
Cellular mobile wireless network 1 is composed of various units 10,
20, 25, 30, 35, 50, 55, 60, which are physically connected
together. FIG. 1 shows a mobile station 10 of mobile wireless
network 1, which may be designed, for example, as a mobile
telecommunications terminal. Mobile telecommunications terminal 10
is connected via a first air interface 90 to a first base station
25 of mobile wireless network 1. First base station 25 is connected
by a first fixed network connection 81 to a first higher-level
network unit 50. A second base station 30 is connected by a second
fixed network connection 82 to a second higher-level network unit
55. A third base station 20 is connected by a third fixed network
connection 80 to first higher-level network unit 50. A fourth base
station 35 is connected by a fourth fixed network connection 83 to
second higher-level network unit 55. First higher-level network
unit 50 is connected by a fifth fixed network connection 85 to a
highest network unit 60. Second higher-level network unit 55 is
connected by a sixth fixed network connection 86 to highest network
unit 60. Optionally, first higher-level network unit 50 may be
connected via a seventh fixed network connection to second
high-level network unit 55, as indicated with dotted lines in FIG.
1. First higher-level network unit 50, second higher-level network
unit 55 and optionally additional high-level network units form
"radio network subsystems" (RNS) according to the UMTS standard.
The highest network unit thus form a "GPRS support node" (General
Packet Radio System Support Node) (GSN) according to the UMTS
standard.
In cellular mobile wireless network 1, logical connections are
established for data transmission between mobile telecommunications
terminal 10 and the other units of mobile wireless network 1
involved in the connection thus established. There are various
types of logical connections between mobile telecommunications
terminal 10 and the various participating units of mobile wireless
network 1 at the same time. These logical connections originate
from a hierarchical model in which each hierarchical layer
corresponds to a protocol present in both mobile telecommunications
terminal 10 and the corresponding unit of mobile wireless network 1
and implements the corresponding logical connection.
FIG. 2 illustrates exemplary logical connections between mobile
station 10 and first higher-level network unit 50, as well as
connections between mobile station 100 and first base station 25.
The lowest hierarchical layer in this hierarchical model is formed
by a first physical layer 110 in mobile telecommunications terminal
10 and a second physical layer 115 in first base station 25, which
implement a physical connection corresponding to first air
interface 90 between mobile telecommunication terminal 10 and first
base station 25 of mobile wireless network 1. Above this, there is
a data security layer (also referred to according to the UMTS
standard as a "data connection layer") and is divided into multiple
sublayers and implements various logical connections between mobile
telecommunications terminal 10 and first higher-level network unit
50, which is designated as a "radio network controller" (RNC)
according to the UMTS standard. Such a sublayer is referred to,
according to the UMTS standard, as the wireless connection control
layer, also known as "radio connection control" layer (RLC), in
which a first RLC protocol 120 in mobile telecommunications
terminal 10 and a second RLC protocol 25 in first higher-level
network unit 50 implement a first logical RLC connection 101 as one
of the aforementioned logical connections. Another sublayer is
referred to as the "packet data convergence protocol" layer (PDCP)
according to the UMTS standard. In this sublayer, a first PDCP
protocol 130 in mobile telecommunications terminal 10 and a second
PDCP protocol 135 in the first higher-level network unit 55
implement a first logical PDCP connection 102. Additional
protocols, such as the Radio Resource Control (RRC) protocol, the
Internet Protocol IP, the Transit Control Protocol (TCP) and the
like may establish additional logical connections in the higher
hierarchical layers such as the network layer and the transport
layer. As shown in FIG. 2, adjacent layers in the hierarchical
model are connected together, with higher-level layers using the
services of the respective adjacent lower-level layers. Second
physical layer 115 is connected via the first fixed network
connection to first higher-level network unit 50, as shown in FIG.
1, and is connected to second RLC protocol 125.
The publication "Technical Specification 25.301, UMTS Radio
Interface Protocol Architecture" refers to the corresponding UMTS
protocol architecture of layers 2 and 3, which also include the
packet data convergence protocol layer. For example, this
publication refers to the packet data convergence protocol layer
and its position within this architecture. The publication
"Technical Specification 25.323 refers to PDCP protocol 130, 135,
Packet Data Convergence Protocol".
One function of PDCP protocol 130, 135 is to compress packet data
control information, which has been added by the protocols of the
transport layer and network layer situated above the packet data
convergence protocol layer to the user data, which has also been
combined into data units or packet data units in the packet data
protocol layer before its transmission, of an application which is
also running at a higher level than the packet data convergence
protocol layer and which should be compressed before transmission
via first air interface 90 to permit efficient transmission.
This compression may be accomplished in various ways. Compression
algorithms are specified, for example, in the publication IETF, RFC
1144 or in the publication IETF, RFC 2507. Most efficient
compression algorithms make use of the fact that there is little or
no difference in the packet data control information in successive
packet data units of a certain data type. Differential coding is
used for the packet data control information, decompressing the
packet data control information of the first packet data unit of a
first data type or of other reference packet data and transmitting,
for all other packet data units of this data type, the difference
in comparison with the preceding packet data control information or
other reference packet data control information. The data types of
the packet data units may be, for example, the transport and
network layer protocols used. For example, a first type of data may
be predefined by a TCP/IP protocol and a second type of data may be
predefined by a UDP/IP protocol (User Datagram Protocol).
To permit efficient encoding or compression of the packet control
information even when a packet data stream is composed of packet
data units of different types of data, a table is created on the
receiving end and the transmitting end during encoding with the
packet data control information of the various types of data being
stored in this table. For each packet data unit to be compressed,
it is first checked in the table whether a similar or identical
entry has already been stored there. If this is the case, then the
differential coding is executed between the new packet data control
information and that in the table and the information transmitted
to the decompressor or the receiving end includes not only the
difference, but also reference to the table entry for which the
differential coding has been used. If no suitable entry is found on
the transmitting end in the table, the packet data unit is
interpreted as a new type of data. In addition, the respective
packet data control information is included as a new entry in the
table and transmitted without compression. The receiver also
includes this packet in its table.
For efficient compression of packet data control information of
packet data streams, tables which are also referred to as
compression tables or code books, are created during compression on
the transmitting end and on the receiving end. These code books
make it possible for the differential coding described here to be
implemented. To be able to decode such differentially coded packet
data control information, the tables on the transmitting end and
the receiving end must always be identical.
The cellular mobile wireless network offers the possibility of data
transmission from mobile telecommunications terminal 10 to a unit
of mobile wireless network 1 even if the user of mobile
telecommunications terminal 10 leaves the wireless cell which is
covered by first base station 25. To do so, a method of transfer of
the connection thus established for data transmission from first
base station 25 to second base station 30 is implemented between
mobile telecommunications terminal 10 and mobile wireless network
1, assuming that the user of mobile telecommunications terminal 10
is moving into the wireless cell covered by second base station 30.
This change in connection as described here is also referred to as
"relocation."
When relocation occurs, it may now happen that second base station
30 to which the connection is to be transferred may be connected to
a different higher-level network unit than the previous first base
station 25. This is the case in the exemplary embodiment described
here, according to which second base station 30, in contrast with
first base station 25, is connected to second higher-level network
unit 55.
Each protocol always exists at least twice on the same protocol
layer level in different network units, just as the RLC protocol
and the PDCP protocol in FIG. 2 exist in both mobile
telecommunications terminal 10 and in first higher-level network
unit 50. Specifically PDCP protocols 131, 135 are implemented in
mobile telecommunications terminal 10 according to the UMTS
standard as described above and also in first higher-level network
unit 50 as well as in additional higher-level network units, which
are designed as RNC. In the case of the relocation described here,
the existing data connection between mobile telecommunications
terminal 10 and mobile wireless network 1 is shifted so that it
runs over second base station 30 and second higher-level network
unit 55. Thus, before the relocation, first PDCP protocol 130 in
mobile telecommunications terminal 10 transmits to second PDCP
protocol 135 in first higher-level network unit 55 over first
logical PDCP connection 102, and after the relocation, it transmits
to a third PDCP protocol 136 of second higher-level network unit 55
according to FIG. 3.
The problem is that during encoding of the packet data control
information in first higher-level network unit 50 by second PDCP
protocol 135, a code book has been created which is not initially
available in second higher-level network unit 55 and therefore is
not usable by third PDCP protocol 136 there. Then if packet data
control information is differentially coded by first PDCP protocol
130 in mobile telecommunications terminal 10 using the code book
created in mobile telecommunications terminal 10, the corresponding
packet data control information cannot be decoded or decompressed
by third PDCP protocol 136 of second higher-level network unit 55
because there is no code book there or the entries in the code book
which is there do not match those in mobile telecommunications
terminal 10.
One answer to this problem is to reset the PDCP protocol units
provided for creation of the required PDCP profiles in second
higher-level network unit 55 and in mobile telecommunications
terminal 10. Nothing need be done for this in second higher-level
network unit 55 because the corresponding PDCP protocol unit there
is reestablished with each change in connection and therefore is
automatically reset. In mobile telecommunications terminal 10,
however, the corresponding PDCP protocol unit must be reset
explicitly, and all the code books it has used must be deleted and
the first PDCP protocol 130 reset to its original state. This
method has the disadvantage that after a change in connection, it
is necessary to recreate code books in second higher-level network
unit 55 and in mobile telecommunications terminal 10, and the first
packet data control information of each type of data to be encoded
is at first decoded and decompressed and is thus transmitted
inefficiently.
Thus, the present invention the transmission of
transmission-specific information such as code books created during
a connection, in a change of connection from first higher-level
network unit 52 to second higher-level network unit 55.
This has the advantage that efficient transmission over a second
air interface 90 according to FIG. 1 is also possible even after
the relocation without having to first transmit the first packet
data control information of each type of data in decoded and thus
decompressed form. The transmission-specific information is
transmitted from first higher-level network unit 50 either directly
over seventh fixed network connection 87 or over fifth fixed
network connection 85, highest network unit 60 and sixth fixed
network connection 86 to the second higher-level network unit when
changing connection. The resulting increased burden on
aforementioned fixed network connections 85, 86, 87 when changing
connection is not significant because in the case of small code
books, the amount of data to be transmitted is small and fixed
network connections 85, 86, 87 allow the use of a much higher data
rate than second air interface 91 between mobile telecommunications
terminal 10 and second base station 30.
In addition, it is also possible, before or during establishment of
the connection on the part of mobile telecommunications terminal 10
of first higher-level network unit 50, to provide for signaling
whether in the case of a relocation the transmission-specific
information is to be transmitted from first higher-level network
unit 50 to the corresponding new higher-level network unit or
whether the PDCP protocol unit in mobile telecommunications
terminal 10 is to be reset as described. It is also possible for
first higher-level network unit 50 to send a signal to mobile
telecommunications terminal 10 to indicate whether in the case of a
relocation the transmission-specific information is to be sent from
first higher-level network unit 50 to second higher-level network
unit 55. Corresponding signaling information may be added to a
message transmitted from first higher-level network unit 50 to
mobile telecommunications terminal 10 to make a wireless
transmission carrier available for the connection to be
established, this message also being designated as a "radio bearer
setup" message according to the UMTS standard.
Another possibility is to perform corresponding signaling
immediately before or during the relocation to be implemented.
An exemplary embodiment according to the present invention is thus
based on a concrete and exemplary scenario in which mobile
telecommunications terminal 10 is connected to units of mobile
wireless network 1 such as first base station 25, first
higher-level network unit 50 and highest network unit 60 via the
required physical and logical connections, in particular first
logical PDCP connection 102 implemented by first PDCP protocol 130
and second PDCP protocol 135 between mobile telecommunications
terminal 10 and first higher-level network unit 50, and a transfer
of data, i.e., an exchange of packet data units, is taking place
over these connections.
Because of their functionality, first PDCP protocol 130 and second
PDCP protocol 135 store information which is needed for compression
and manipulation of user data and packet data control information.
To permit proper functioning of these two PDCP protocols 130, 135,
a portion of this transmission-specific information in the two PDCP
protocols 130, 135 must be synchronized or must even be identical.
If mobile telecommunications terminal 10 then changes the wireless
cell in mobile wireless network 1, e.g., because of the movement of
mobile telecommunications terminal 10 out of the transmission range
of first base station 25 into a new wireless cell, a relocation is
implemented and a new physical connection is established between
mobile telecommunications terminal 10 and second base station 30,
which covers the new wireless cell. This new physical connection
corresponds to second air interface 91 according to FIGS. 1 and 3.
FIG. 3 illustrates the connection of mobile telecommunications
terminal 10 to second higher-level network unit 55 over second base
station 30, with the same reference numbers denoting the same
elements as in FIG. 2. Second base station 30 according to FIG. 3
is connected to second higher-level network unit 55 or its RLC
protocol, which is identified here as third RLC protocol 126, over
second fixed network connection 82. Second higher-level network
unit 55 is structured like first higher-level network unit 50 and
has third PDCP protocol 136 accordingly in addition to third RLC
protocol 126. Second base station 30 is connected to second
higher-level network unit 55 which is different from first
higher-level network unit 50 in mobile wireless network 1, as
described above. The logical connections between mobile
telecommunications terminal 10 and second higher-level network unit
55 are thus also established anew. A second logical RLC connection
103 is established between first RLC protocol 120 and third RLC
protocol 126. A second logical PDCP connection 104 is established
between first PDCP protocol 130 and third PDCP protocol 136. First
logical PDCP connection 103 is thus replaced by second logical PDCP
connection 104. To do so, third PDCP protocol 136 must first be
generated anew in second higher-level network unit 55 after the
relocation.
To now permit a correct data flow over second logical PDCP
connection 104, first PDCP protocol 130 must first be synchronized
again in mobile telecommunications terminal 10 and third PDCP
protocol 136 must be synchronized again in second higher-level
network unit 55. A method of doing so is to reset first PDCP
protocol 130 in mobile telecommunications terminal 10 to a defined
starting state, which corresponds to the starting state of third
PDCP protocol 136 which is created anew with the relocation,
whereupon first PDCP protocol 130 and third PDCP protocol 136 then
contain the same transmission-specific information.
An exemplary embodiment according to the present invention,
however, proposes a method in which the transmission-specific
information of second PDCP protocol 135 is transmitted from first
higher-level network unit 50 to a third PDCP protocol unit in
second higher-level network unit 55 to produce a third PDCP
protocol 136 having the transmission-specific information of second
PDCP protocol 135. Then it is not necessary to reset first PDCP
protocol 130. Therefore, the compression methods of first PDCP
protocol 130 and second PDCP protocol 135 may also be applied
continuously between first PDCP protocol 130 and third PDCP
protocol 136 without resetting the latter two PDCP protocols 130,
136. This results in a considerable data reduction at second air
interface 91 in comparison with resetting first PDCP protocol 130
and third PDCP protocol 136 because the transmission-specific
information need not be created anew and gradually transmitted over
second air interface 91 only to achieve the same or a similar
status of the transmission-specific information in first PDCP
protocol 130 and in third PDCP protocol 136 as that achieved at the
end of the connection of mobile telecommunications terminal 10 with
second higher-level network unit 55.
Now the relevant methods when changing connection from the wireless
cell of first base station 25 to the wireless cell of second base
station 30 will be described as an example.
In establishing the connection between mobile telecommunications
terminal 10 and units 50, 60 of mobile wireless network 1 via first
base station 25, various parameters for establishing the connection
between these units 50, 60 of mobile wireless network 1 and mobile
telecommunications terminal 10 will be discussed. These parameters
also include the compression algorithm used for compression of the
protocol control information, the allowed length of the code books
and the quality service of the connection.
According to an exemplary embodiment of the present invention,
another parameter, which defines whether the PDCP protocol created
in the new higher-level network unit is to be reset when changing
connection from the first higher-level network unit 50 to a new
higher-level network unit which is different from the first
higher-level network unit or whether the transmission-specific
information present and already built up is to be transmitted from
first higher-level network unit 50 to the new higher-level network
unit may be added to this parameter negotiation. The signaling
required accordingly for the parameter negotiation may in the
simplest case be accomplished with one bit which is added to a
message to be sent to first higher-level network unit 50 for the
parameter negotiation or which is added to a message to be sent
from first higher-level network unit 50 for the parameter
negotiation and whose two states signal the information "PDCP
protocol is reset" or "transmission-specific information is
transmitted when relocation takes place." In this example, the bit
is set at "transmission-specific information is transmitted when
relocation takes place."
Packet data units generated by an application are transferred in
first higher-level network unit 50 by a TCP protocol and an IP
protocol to the corresponding PDCP protocol unit, which is at a
lower level in the layer sequence, which compresses it and next it
is transferred to corresponding second RLC protocol 125 which is at
a lower level in the layer sequence of the PDCP protocol unit. The
packet data units are in addition stored in a buffer memory 160 in
the PDCP protocol unit of first higher-level network unit 50
according to FIG. 4b until the RLC unit of first higher-level
network unit 50 which is responsible for the implementation of
second RLC protocol 125 acknowledges the correct transmission of
the packet data units to mobile telecommunications terminal 10. Let
us assume that (m-1) packet data units have been transferred in
compressed form by PDCP protocol unit of first higher-level network
unit 50 to its RLC unit and acknowledged by this before the point
in time when the relocation takes place. Another six packet data
units m, m+1, . . . , m+5 have also been transferred to this RLC
unit, but have not been acknowledged and are therefore still in
buffer memory 160. Packet data units m, m+1, . . . , m+5 here are
labeled with reference notation 161, 162, 163, 164, 165, 166. In
compression of the packet control information, a code book 150 has
been created as a compression table, which in this example has n
entries according to FIG. 4a, labeled with reference numbers 151,
152, 153, 154, 155, 156, 157.
At the time when the relocation initiated by first higher-level
network unit 50 or mobile telecommunications terminal 10 is to take
place, the protocols necessary to maintain the data transmission,
such as third RLC protocol 126 and third PDCP protocol 136, are
generated in second higher-level network unit 55 as the new
higher-level network unit after the relocation.
Then, according to an exemplary embodiment of the present
invention, the updated transmission-specific information stored in
the PDCP protocol unit of first higher-level network unit 50, i.e.,
in this example code book 150, and the content of buffer memory 160
are transmitted from first higher-level network unit 50 to second
higher-level network unit 55. To do so, seventh fixed network
connection 87 between the two higher-level network units 50, 55 may
be used if it exists or the transmission-specific information may
be sent from first higher-level network unit 50 to second
higher-level network unit 55 over fifth fixed network connection
85, highest network unit 60 and sixth fixed network connection 86.
After the transmission-specific information has been sent to third
PDCP protocol 136, this third PDCP protocol 136 represents an exact
copy of second PDCP protocol 135 of first higher-level network unit
50 directly before the relocation with regard to second logical
PDCP connection 104 between PDCP protocol units of mobile
telecommunications terminal 10 and second higher-level network unit
55, and the data transmission of the packet data units may be
started again essentially directly or continued from the state, as
it existed most recently before the relocation.
For the transmission-specific information to be transmitted from
first higher-level network unit 50 to second higher-level network
unit 55, code book 150 and the content of buffer memory 160 are
mentioned only as examples. Similarly, the transmission-specific
information to be transmitted may alternatively or additionally
also contain other information, e.g., information regarding
compression of the user data in the packet data units to be
transmitted within the framework of the connection established,
this information actually being formed by code books
accordingly.
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